Posted by **Sandy** on Saturday, March 31, 2012 at 2:07pm.

What is the domain of

f(x) = √(x^2-2x-8)

Thanks!

- Math -
**Bosnian**, Saturday, March 31, 2012 at 3:27pm
When the leading coefficient a is positive, the parabola opens up ( concave up )

For function:

x ^ 2 - 2 x - 8

the leading coefficient is a = 1

function is concave up

When the parabola ia concawe up all walues between roots are negative.

No negative number can have a real square root.

Funtions zerro points are :

- 2 and 4

So domain of your fuction:

( - infinity , -2 ] U [ 4 ,infinity )

OR

x <= -2 and x >= 4

If you dont knowe how to solve equation:

x ^ 2 - 2 x - 8 = 0

In google type:

quadratic equation online

When you see list of results click on:

Free Online Quadratic Equation Solver:Solve by Quadratic Formula

When page be open in rectangle type:

x ^ 2 - 2 x - 8 = 0

and click option: solve it!

You wil see solution step-by-step

If you want graph of functions:

Go on :

wolframalpha dot com

When page be open in rectangle type :

x ^ 2 - 2 x - 8

and click option =

after few seconds yo will everythig about function

Then type :

sqrt ( x ^ 2 - 2 x - 8 )

and click option =

P.S.

Sorry for My bad English

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